Loud speaker



July 12, 1938; J. M w. STONE v21212354142 LOUD SPEAKER Filed July 24,1936 2 Sheets-Sheet 1 July 12, 1938. J. Mew. STONE 2,123,442

LOUD SPEAKER Filed July 24, 1936 2 Sheets-Sheet 2 FREQUENCY IN C.P.5.

Patented July 12, 1938 UNiTE STATES F'EENT @FFHQE LOUD SPEAKER linoisApplication July 24, 1936, Serial No. 92,350

5 Claims.

The invention relates to loud speakers and has among its other objectsthe provision of a loud speaker which has improved means whereby it maybe adjusted with fidelity or to emphasize the desired range of tones.

Another object of the invention is to provide a loud speaker havingimproved means whereby it may be adjusted in relation to the acousticsof a room so that it reproduces sound in a desired manner.

Still another object of the invention is to provide improved meanswhereby a loud speaker may be quickly and easily adjusted to reproducesound in a desired manner.

Other objects and advantages will become apparent as the followingdetailed description progresses, reference being had to the accompanyingdrawings, wherein- Fig. 1 is a longitudinal section taken through a loudspeaker which embodies the invention.

Fig. 2 is an enlarged fragmentary section taken on the same line as Fig.1.

Fig. 3 is a section taken on line 33 of Fig. 1, and

Fig. 4 is a diagram illustrating the manner in which the improved loudspeaker operates when it is adjusted to operate in two diiTerent Ways.

Referring for the present to Figs. 1 to 3, inclusive, wherein apreferred embodiment of the invention is illustrated, the referencecharacter it designates the front wall of a cabinet of the type commonlyemployed to house radio receivers. It will be readily understood thatthe wall Ill functions as a bafile. A loud speaker designated generallyby the reference character II is in registry with an opening l2 providedin the wall it. The loud speaker ll comprises a diaphragm or cone i3formed of any suitable substance such as paper or fabric. Secured to thecone it at the smaller end thereof is a sleeve i5 which carries thevoice coil it. The sleeve i5 and the voice coil 58 reciprocatelongitudinally of the loud speaker and longitudinally with respect to acentral pole piece H which is secured at its rear end to a U-shapedmember it forming part of an electro-magnet. The winding of theelectromagnet is not shown. Secured to the U-shaped member i8 is anouter pole piece or plate which co-operates with the central pole piecell to form the annular magnetic gap in which the voice coil 56reciprocates. The memher is and the outer pole piece 28 are secured toeach other and to a metallic basket 22 by a plurality of bolts 24, thebasket 22 being provided with the usual apertures 25 so as to reduce theamount it will damp the action of the cone l3.

The basket 22 terminates at its periphery in an annular flange 26, theconstruction being such that an annular shoulder 21] is formed againstwhich the periphery of the cone i3 abuts. In- 5 terposed between theperiphery or marginal portion of the cone l3 and the inner surface ofthe wall l are a plurality of cardboard rings 28, or the equivalent,which are glued to each other and to the periphery of the cone. The coneIS, the 10 basket and the cardboard rings 28 are secured to the wall itby means comprising a plurality of screws and a plurality of posts 32which are screw-threaded upon shanks of the screws 38 (Fig. 2). It willbe noted that the screws 3%? oo- 15 operate with the posts 32 to clampthe cardboard rings 28 and the marginal portions of the cone i3 and thebasket 22 between the posts and the wall it. The inner ends of the posts32 have screws 33 screw-threaded therein. The screws 33 secure washers34 to the inner ends of the posts 32.

Slidably journalled upon the posts 32 are grommets 36 which arepreferably formed from rubber and are provided with annular grooves 37whereby they are secured to a housing member or shell 43. It will benoted that when the shell 49 is in the position wherein it is shown infull lines in Fig. 1, it provides a relatively large chamber in back ofthe basket 22 and it will also be noted that the back end of the shell59 is spaced a relatively large distance from the magnet structure whichcomprises the central and outer poles H and 2c, respectively, and themember i8. Secured to the back wall of the shell is a rod or plunger ll,the plunger ii being provided with a knob 42 in back of the shell 46 andbeing provided with a knob 13 within the cone 53 so that it isaccessible tln-ough the hole i2 provided in the wall ill. The back wallof the shell 4B is clamped between the knob 32 and a washer 4 a nut 5screw-threaded upon the plun er being provided to secure these partstogether. The knob 43 is screw-threaded upon the plunger.

The plunger ll projects through a bore 53 extending longitudinally andcentrally through the central or inner core ill, the bore being linedwith felt 52 so that the metallic plunger 4! will not contact the metalof the inner core ii and thereby affect the reproducing characteristicsof 5.0 the loud speaker.

It will be readily understood that one may grasp the knob 42 and drawthe shell 4-8 and the plunger ll into positions wherein they are shownin dotted lines in Fig. 1. Such displacement of 55 the shell 50 and theplunger M is permitted by the grommets 36 which slide upon the posts 32.

The marginal portions at the forward end of the shell 40 preferablycomprise a cylindrical internal flange and an outwardly extendingannular flange 5'5. When the shell 40 is in the position wherein it isshown in dotted lines in Fig. 1, the cylindrical flange 55 encircles theflange 26 of the basket member 22.

Glued or otherwise secured to the smaller end of the basket 22, is afelt ring 58. A damping member 68 which is preferably formed fromcardboard and is preferably in the shape of a truncated cone, has itsbase portion secured to the forward end of the shell M by glue or othersuitable means. The inner or smaller end of the damping member 68terminates in a bead 63 so that the inner edge of the clamping member68) may engage the felt ring 58 yieldingly.

When the shell 69 is displaced from the position wherein it is shown inFig. 1 to the position wherein it is shown in dotted lines in the samefigure, or to any intermediate position, the damping member 68 isadjusted into a corresponding position as indicated by dotted lines inFig. 1. Of course, such adjustment may be made by pulling or pushing, asthe case may be, on the knob 32 or the knob 33.

When the damping member 65 is in the position wherein it is shown infull lines in Fig. 1, it exercises the'maximum of damping effect uponthe cone !3 and when the damping member is in the position wherein it isshown in dotted lines in Fig. 1, it exercises the minimum of dampingeffect upon the cone is. Obviously, the damping member may be moved toan intermediate position, if desired, to obtain a desired damping effectupon the cone I3.

In Fig. 4 a diagram is shown comprising two graphs W and H. Frequenciesin cycles per second are plotted along the base line 12 of the diagram.The decibel variation in intensity of vibration or sound is plottedalong the vertical line 13. The graph 70 indicates the action of theloud speaker I I when the shell 48 and the damping member are displacedinto the positions wherein they are shown in dotted lines in Fig. 1, itbeing understood that when the damping member 6E1 is inthe positionwherein it is shown in dotted lines in Fig. 1, it has a minimum ofdamping effect upon the cone E3. The graph 11 rep-resents the action ofthe loud speaker or cone when the shell 4!! and the damping member 50are in the positions wherein they are shown in full lines in Fig. 1.

It will be noted that when the damping member is'displaced toward thecone IS, the intensity of the vibrations of the cone l3 at lowfrequencies is diminished while the intensity of the vibrations of thecone I3 is increased in the higher frequencies. Of course, when thedamping member 60 is displaced into positions intermediate the full anddotted line positions of Fig. 1, the action of the cone 13 may berepresented by graphs which will lie mainly between the graphs it] and 1I. In other words, the closer the damping member 60 is brought to thecone IS, the more the low frequencies will be damped and the more theintensity of the high frequencies will be increased.

It will be noted that in graph ii! there is a peak 15 in the lowerfrequencies. This peak corresponds to the natural mechanical period ofthe moving system of the loud speaker. When the damping member 60 isdisplaced toward the cone l3 the peak 15 is diminished more and more. Itwill be noted that the peak has disappeared entirely in the graph H.

It may be mentioned that the energy which is taken from the lowerfrequencies is returned substantially entirely to the higherfrequencies. It maybe said that the energy represented between thegraphs H and 15 at the lower frequencies is substantially equal to theenergy represented between these graphs at the higher frequencies.

While certain embodiments of the invention have been shown anddescribed, it is to be understood that it is capable of manymodifications. Changes, therefore, in the construction and arrangementmay be made without departing from the spirit and scope of the inventionas disclosed in the appended claims in which it is the intention toclaim all novelty inherent in the invention as broadly as possible inView of the prior art.

Having thus described the invention, what I claim as new and desire tosecure by Letters Patent is:

l. A loud speaker comprising an apertured bafiie, a diaphragm mounted onsaid baffle in registry with the aperturetherein, means for actuatingsaid diaphragm, a housing member providing a chamber in back of saiddiaphragm, means mounted on said baffle for adjustably mounting saidhousing member thereon and means disposed in said housing member andmovable therewith for damping the diaphragm.

2. A loud speaker comprising an apertured bafiie, a diaphragm mounted onsaid baflle in registry with the aperture therein, means for actuatingsaid diaphragm, a housing member providing a chamber in back of saiddiaphragm,

means mounted on said baffle for adjustably mounting said housing memberthereon, and an apertured member disposed in said housing member andmovable therewith for damping the dia phragm.

3. A loud speaker comprising an aperture-d baflie, a diaphragm mountedon said bafiie in registry with the aperture therein, means foractuating said diaphragm, a housing member providing a chamber in backof said diaphragm, means mounted on said baifle for adjustably mountingsaid housing member thereon, and a damping member extending transverselyof said housing and having a central aperture in registry with thecentral portion of said diaphragm, said damping member being movablewith said housing to control the sound reproduction of said diaphragm.

4. Means for damping a substantially conical diaphragm, said .meanscomprising a housing member disposed'in back of said diaphragm, meansadjustably mounting said housing member,

and a frustro-conical member disposed in said.

housing and movable therewith for controlling the sound reproduction ofthe diaphragm.

5. Means for damping a substantially conical diaphragm, said meanscomprising a housing disposed in back of said diaphragm, meansadjustably mounting said housing, andafrustro-conical mem ber disposedin said housing and movable therewith for controlling the soundreproduction of the diaphragm, the axes of said conical diaphragm andsaid frustro-conical member being coincident and said frustro-conicalmember having a central opening. 77

JOHN MCWILLIAMS STONE.

